Chainsaw question

[TNhobbyfarmer]

First a little background. My old trusty Stihl 025 recently started running very hot. After a few minutes of use, smoke would seep out from under the sprocket cover and the bar and chain would get very hot to the touch. Cutting would become very difficult even with a new chain. I thought it was a bar oil pump problem, but I determined that the chain was getting adequate lubrication. Since the saw is pretty old, and I suspect a trip to the shop would probably get pretty pricey, I decided to purchase a new saw, another Stihl.

I decided to read the manual of the new saw to possibly learn something new. The section on fuel indicated something quite interesting. It said that if you change from fuel with ethanol to non ethanol fuel or vice versa it will cause the saw to run hot. That's exactly what I recently did. I have heard so much about how bad ethanol is for small engines, I switched over to non ethanol. Could that possibly be the problem? Do any of you have knowledge of this phenomenon?

I am thinking of mixing up a gallon of ethanol fuel and see if the old Stihl cools down and starts operating properly again. Give me your thoughts. It kinda sounds odd to me, but I feel confident that the engineers at Stihl know of what they speak.

 

[wmonroe]

I can't see how changing fuels would affect it unless the carb was adjusted for the specific fuel, but those engineers are much smarter than me. Does it have a chain brake, any chance it's not fully released?

 

[s219]

Your 025 probably had a toasted bearing or clutch problem, or perhaps the brake was sticking (even slightly can cause what you describe). Bearing, clutch, and brake are all in the same area and would all put smoke out from under the clutch cover.

The only way fuel can make a saw run hot is if it creates a lean condition. I have no idea how changing fuel types would cause that unless you have a model that has the electronic carb/tune, in which case it's possible it would take the saw a little while to re-learn a tune if the fuel was different enough. But I still can't imagine it would run lean for very long, or that changes in fuel type would be a significant issue.

I can tell you I have run all my saws interchangeably on ethanol and non-ethanol fuel, including two pro Stihls (neither with electronic carb/tune). One is used for milling, which means long high-RPM cuts in the wood under load. I have never noticed any difference in saw temperature with the fuel changes.

 

[MinnesotaEric]

First a little background. My old trusty Stihl 025 recently started running very hot. After a few minutes of use, smoke would seep out from under the sprocket cover and the bar and chain would get very hot to the touch. Cutting would become very difficult even with a new chain. I thought it was a bar oil pump problem, but I determined that the chain was getting adequate lubrication. Since the saw is pretty old, and I suspect a trip to the shop would probably get pretty pricey, I decided to purchase a new saw, another Stihl.

I decided to read the manual of the new saw to possibly learn something new. The section on fuel indicated something quite interesting. It said that if you change from fuel with ethanol to non ethanol fuel or vice versa it will cause the saw to run hot. That's exactly what I recently did. I have heard so much about how bad ethanol is for small engines, I switched over to non ethanol. Could that possibly be the problem? Do any of you have knowledge of this phenomenon?

I am thinking of mixing up a gallon of ethanol fuel and see if the old Stihl cools down and starts operating properly again. Give me your thoughts. It kinda sounds odd to me, but I feel confident that the engineers at Stihl know of what they speak.

Ethanal can screw up the rubber bits in a carb not designed to run it, thereby changing your mixture. Tuning wise, if an engine is running hot (but still running), then it is running lean and needs to have the mixture richened.

Anyway, I run zero ethanol in any of my small engines and run ethanol laced fuel only under duress in cars and trucks. Ethanol get worse mpg and washes the oil film off of the cylinder bore increasing wear and tear. This is especially true of small engines, none of which are designed (as a preferred fuel type) to run ethanol mixed fuel, although many can run up to a 15% ethanol blend. I use non-oxgenated fuels in my small engines as a rule. Since Stihl has good dealers, I'd call the dealer who sold you the saw and ask what the saw was set up to run and if there are any concerns you should have going forward.

 

[2458n]

I have the newer MS250C and it smokes under the cover, but it is coming from burning paint off the bar. The saw is the first stihl I have had that does not have a method to increase the oil flow to the bar. The oil is there but the bar is already ruined. I would not recommend this new saw as a replacement.

 

[TomSeller]

Your 025 probably had a toasted bearing or clutch problem, or perhaps the brake was sticking (even slightly can cause what you describe). Bearing, clutch, and brake are all in the same area and would all put smoke out from under the clutch cover.

The only way fuel can make a saw run hot is if it creates a lean condition. I have no idea how changing fuel types would cause that unless you have a model that has the electronic carb/tune, in which case it's possible it would take the saw a little while to re-learn a tune if the fuel was different enough. But I still can't imagine it would run lean for very long, or that changes in fuel type would be a significant issue.

I can tell you I have run all my saws interchangeably on ethanol and non-ethanol fuel, including two pro Stihls (neither with electronic carb/tune). One is used for milling, which means long high-RPM cuts in the wood under load. I have never noticed any difference in saw temperature with the fuel changes.

I agree with this. A change in fuel will not create a hot spot in the brake area. Take a closer look at the old saw and maybe you can determine what it is, fix it, and have a good backup saw.

 

[KiotiKowboy]

I have the newer MS250C and it smokes under the cover, but it is coming from burning paint off the bar. The saw is the first stihl I have had that does not have a method to increase the oil flow to the bar. The oil is there but the bar is already ruined. I would not recommend this new saw as a replacement.

Have you considered running a lighter weight oil?

 

[2458n]

running Stihl oil in the orange jug. It has not been below freezing when I am cutting and I am using same oil in ms440.

 

[MinnesotaEric]

I have the newer MS250C and it smokes under the cover, but it is coming from burning paint off the bar. The saw is the first stihl I have had that does not have a method to increase the oil flow to the bar. The oil is there but the bar is already ruined. I would not recommend this new saw as a replacement.

Wow, that's too bad. I'm really pleased with my MS250C-BE that I wanna say I purchased new in 2009. I've cut down hundreds of trees with it and compression remains good, the bar is still original (although I do oil the idle wheel and use Stihl's own bar oil) and I'm nearing the end of life of the second set of chains (they can only be sharpened so many times). I'm on my second spark plug and my third air filter. What is really nice, is that the saw still starts easily in silly cold weather with the choke and that the saw warms up quickly. Super happy with it and I'd buy it again, and again, with both hands.

 

[dodge man]

I have had my saw get hot like you describe. Usually if I take it apart and clean around the clutch area and get all the saw dust out it helps. Ethanol and non ethanol switching back and forth causing problems? I don't buy it.